Only the kernel of Hideo Yokoyama's 2004 novel remains in this manga version
of Deguchi no nai umi (Sea without exit). This manga story, directed
mainly at teenage girls, has a completely different atmosphere than Yokoyama's
novel and the popular
film with the same title released in 2006. The book
focuses almost entirely on the romantic relationship of Koji Namiki, who dies
while training in a kaiten human torpedo, and Minako Narumi, who continues to
strongly love Namiki during his time away in the Navy and even after his death.

Namiki, a pitcher on a Tokyo university baseball team, searches for a
"magic pitch" (makyu in Japanese) that will have differences in
the first part and last part of the pitch. However, he soon leaves the
university to join
the Navy and to become a kaiten (human torpedo) pilot. Namiki goes on a special
attack (suicide) mission with a submarine carrying four kaiten, but his kaiten
fails to launch when an enemy ship is sighted, so he returns to base. Later
during a training exercise his kaiten disappears and cannot be found. In 1945
soon after the end of the war, Namiki's kaiten washes up on shore after
a typhoon. His friend Katsuya Kita, who was a member of the track club at
Namiki's university and his kaiten squadron leader, finds Namiki's letter to
Minako and a baseball with the following words written on it, "the magic
pitch is completed."

This manga depicts a much more explicit romantic relationship between Namiki
and Minako than that in the book and movie. The manga story also includes
several incidents not mentioned in either the book or film such as the following
ones. Minako gives Namiki a little mascot doll dressed as a baseball player with
his number 18 on the uniform. This doll shows up throughout the story, and he
takes it with him in his kaiten. She tells him that her favorite poem
from Manyoshu ("Ten Thousand Leaves," the oldest existing
anthology of Japanese poetry dating back to the 7th and 8th centuries) is one
that describes a woman who, rather than thinking about the man who leaves her
behind, asks him to please leave signs along the road so she can follow him. In
2006 at the end of the story, Minako and Kita meet at the university where Namiki
played
baseball. The baseball club's trophy case displays Namiki's baseball marked "the
magic pitch is completed." Minako and Kita cheer the
modern-day baseball team, and the spirit of Namiki says in the last frame of the
comic, "I am living in the world that you two left for me."

Deguchi no nai umi (Sea without exit), which takes up about two
thirds of the pages in this manga book with one other story at the end, provides little insights into the
motivations of the three main characters of Namiki, Minako, and Kita. Minako's
starry-eyed love of Namiki encounters no conflicts in their relationship, whereas the
novel portrays their love much more subtly and describes how Namiki becomes
emotionally detached from Minako as he immersed himself in kaiten training. The
manga story also barely mentions or does not include many minor characters who
played important roles in the book and movie. Kita finds Namiki's kaiten in this story, but Namiki's
friend and fellow kaiten pilot Okita, not even mentioned in the manga, finds it
in the novel. The author of this manga story with so few details may have
assumed that a reader would have already known the basic story from viewing the
film in a theater.